Memory cells, methods of operation and fabrication, semiconductor device structures, and memory systems

ABSTRACT

A magnetic cell core includes at least one stressor structure proximate to a magnetic region (e.g., a free region or a fixed region). The magnetic region may be formed of a magnetic material exhibiting magnetostriction. During switching, the stressor structure may be subjected to a programming current passing through the magnetic cell core. In response to the current, the stressor structure may alter in size. Due to the size change, the stressor structure may exert a stress upon the magnetic region and, thereby, alter its magnetic anisotropy. In some embodiments, the MA strength of the magnetic region may be lowered during switching so that a lower programming current may be used to switch the magnetic orientation of the free region. In some embodiments, multiple stressor structures may be included in the magnetic cell core. Methods of fabrication and operation and related device structures and systems are also disclosed.

TECHNICAL FIELD

The present disclosure, in various embodiments, relates generally to thefield of memory device design and fabrication. More particularly, thisdisclosure relates to design and fabrication of memory cellscharacterized as spin torque transfer magnetic random access memory(STT-MRAM) cells.

BACKGROUND

Magnetic Random Access Memory (MRAM) is a non-volatile computer memorytechnology based on magnetoresistance. One type of MRAM cell is a spintorque transfer MRAM (STT-MRAM) cell, which includes a magnetic cellcore supported by a substrate. The magnetic cell core includes at leasttwo magnetic regions, for example, a “fixed region” and a “free region,”with a non-magnetic region in between. The free regions and fixedregions of STT-MRAM cells may exhibit magnetic orientations that areeither horizontally oriented (“in-plane”) or perpendicularly oriented(“out-of-plane”) with the width of the regions.

The fixed region includes a magnetic material that has a substantiallyfixed (e.g., a non-switchable) magnetic orientation. The free region, onthe other hand, includes a magnetic material that has a magneticorientation that may be switched, during operation of the cell between a“parallel” configuration and an “anti-parallel” configuration. In theparallel configuration, the magnetic orientations of the fixed regionand the free region are directed in the same direction (e.g., north andnorth, east and east, south and south, or west and west, respectively).In the “anti-parallel” configuration the magnetic orientations of thefixed region and the free region are directed in opposite directions(e.g., north and south, east and west, south and north, or west andeast, respectively).

In the parallel configuration the STT-MRAM cell exhibits a lowerelectrical resistance across the magnetoresistive elements, i.e., thefixed region and free region. This state of low electrical resistancemay be defined as a “0” logic state of the MRAM cell. In theanti-parallel configuration, the STT-MRAM cell exhibits a higherelectrical resistance across the magnetoresistive elements, i.e., theregions of magnetic material, e.g., the fixed region and free region.This state of high electrical resistance may be defined as a “1” logicstate of the STT-MRAM cell.

Switching of the magnetic orientation of the free region may beaccomplished by passing a programming current through the magnetic cellcore and the fixed and free regions therein. The fixed region within themagnetic cell core polarizes the electron spin of the programmingcurrent, and torque is created as the spin-polarized current passesthrough the core. The spin-polarized electron current interacts with thefree region by exerting a torque on the free region. When the torque ofthe spin-polarized electron current passing through the core is greaterthan a critical switching current density (J_(C)) of the free region,the torque exerted by the spin-polarized electron current is sufficientto switch the direction of the magnetic orientation of the free region.Thus, the programming current can be used to alter the electricalresistance across the magnetic regions. The resulting high or lowelectrical resistance states across the magnetoresistive elementsenables the write and read operations of the conventional MRAM cell.After switching the magnetic orientation of the free region to achievethe one of the parallel configuration and the anti-parallelconfiguration associated with a desired logic state, the magneticorientation of the free region is usually desired to be maintained,during a “storage” stage, until the MRAM cell is to be rewritten to adifferent configuration (i.e., to a different logic state).

A magnetic region's magnetic anisotropy (“MA”) is an indication of thestrength of its magnetic orientation and, therefore, an indication ofthe magnetic material's resistance to alteration of the magneticorientation. A magnetic material exhibiting a magnetic orientation witha high MA strength may be less prone to alteration of its magneticorientation out of that orientation than a magnetic material exhibitinga magnetic orientation with a lower MA strength.

The amount of programming current required to switch the free regionfrom the parallel configuration to the anti-parallel configuration isaffected by the MA strength of the magnetic regions. A free region witha stronger (i.e., a higher) MA strength may require a greater amount ofprogramming current to switch the magnetic orientation thereof than afree region with a weaker (i.e., a lower) MA strength. However, a freeregion with a weak MA strength is also often less stable during storage.That is, a free region with a weak MA strength is prone to prematurealteration out of its programmed configuration (i.e., the programmedparallel or anti-parallel configuration), particularly when the fixedregion of the MRAM cell has a strong MA strength. Therefore, it is oftena challenge to form an MRAM cell with a free region and a fixed regionhaving MA strengths that enable switching with minimized programmingcurrent without deteriorating the cell's ability to store the programmedlogic state without failure (i.e., without premature switching of themagnetic orientation of the free region).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional, elevational, schematic illustration of amagnetic cell structure including a stressor structure proximate to afree region of an out-of-plane STT-MRAM cell.

FIG. 2A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 1 in a storageconfiguration, the magnetic cell structure including a free regionformed of a magnetic material having positive magnetostriction and apredominantly vertical magnetic orientation.

FIG. 2B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 2A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to vertically expand during switching.

FIG. 2C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 2A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to laterally expand during switching.

FIG. 3A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 1 in a storageconfiguration, the magnetic cell structure including a free regionformed of a magnetic material having negative magnetostriction and apredominantly vertical magnetic orientation.

FIG. 3B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 3A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to vertically contract during switching.

FIG. 3C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 3A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to laterally contract during switching.

FIG. 4 is a cross-sectional, elevational, schematic illustration of amagnetic cell structure including a stressor structure proximate to afree region of an in-plane STT-MRAM cell.

FIG. 5A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 4 in a storageconfiguration, the magnetic cell structure including a free regionformed of a magnetic material having negative magnetostriction and apredominantly horizontal magnetic orientation.

FIG. 5B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 5A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to vertically expand during switching.

FIG. 5C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 5A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to laterally expand during switching.

FIG. 6A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 4 in a storageconfiguration, the magnetic cell structure including a free regionformed of a magnetic material having positive magnetostriction and apredominantly horizontal magnetic orientation.

FIG. 6B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 6A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to vertically contract during switching.

FIG. 6C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 6A in a switchingconfiguration, the magnetic cell structure including a stressorstructure configured to laterally contract during switching.

FIG. 7 is a cross-sectional, elevational, schematic illustration of amagnetic cell structure including an upper stressor structure proximateto a free region and a lower stressor structure proximate to a fixedregion of an out-of-plane STT-MRAM cell.

FIG. 8A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 7 in a storageconfiguration, the magnetic cell structure including a fixed regionformed of a magnetic material having positive magnetostriction and apredominantly vertical magnetic orientation.

FIG. 8B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 8A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to vertically contract during switching.

FIG. 8C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 8A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to laterally contract during switching.

FIG. 9A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 7 in a storageconfiguration, the magnetic cell structure including a fixed regionformed of a magnetic material having negative magnetostriction and apredominantly vertical magnetic orientation.

FIG. 9B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 9A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to vertically expand during switching.

FIG. 9C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 9A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to laterally expand during switching.

FIG. 10A is a cross-sectional, elevational, schematic illustration of amagnetic cell structure in a storage configuration, the magnetic cellstructure including an upper stressor structure proximate to a freeregion and a lower stressor structure proximate to a fixed region of anout-of-plane STT-MRAM cell, the free region and the fixed region formedof magnetic materials having positive magnetostriction.

FIG. 10B is a cross-sectional, elevational, schematic illustration ofthe magnetic cell structure of FIG. 10A in a switching configuration,the upper stressor structure configured to vertically expand duringswitching, and the lower stressor structure configured to verticallycontract during switching.

FIG. 11A is a cross-sectional, elevational, schematic illustration of amagnetic cell structure in a storage configuration, the magnetic cellstructure including an upper stressor structure proximate to a freeregion and a lower stressor structure proximate to a fixed region of anout-of-plane STT-MRAM cell, the free region formed of a magneticmaterial having positive magnetostriction and the fixed region formed ofa magnetic material having negative magnetostriction.

FIG. 11B is a cross-sectional, elevational, schematic illustration ofthe magnetic cell structure of FIG. 11A in a switching configuration,the upper stressor structure and the lower stressor structure configuredto vertically expand during switching.

FIG. 12 is a cross-sectional, elevational, schematic illustration of amagnetic cell structure including an upper stressor structure proximateto a free region and a lower stressor structure proximate to a fixedregion of an in-plane STT-MRAM cell.

FIG. 13A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 12 in a storageconfiguration, the magnetic cell structure including a fixed regionformed of a magnetic material having negative magnetostriction and apredominantly horizontal magnetic orientation.

FIG. 13B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 13A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to vertically contract during switching.

FIG. 13C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 13A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to laterally contract during switching.

FIG. 14A is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 12 in a storageconfiguration, the magnetic cell structure including a fixed regionformed of a magnetic material having positive magnetostriction and apredominantly horizontal magnetic orientation.

FIG. 14B is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 14A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to vertically expand during switching.

FIG. 14C is a partial, cross-sectional, elevational, schematicillustration of the magnetic cell structure of FIG. 14A in a switchingconfiguration, the magnetic cell structure including a lower stressorstructure configured to laterally expand during switching.

FIG. 15A is a cross-sectional, elevational, schematic illustration of amagnetic cell structure in a storage configuration, the magnetic cellstructure including an upper stressor structure proximate to a freeregion and a lower stressor structure proximate to a fixed region of anin-plane STT-MRAM cell, the free region formed of a magnetic materialhaving negative magnetostriction and the fixed region formed of amagnetic material having positive magnetostriction.

FIG. 15B is a cross-sectional, elevational, schematic illustration ofthe magnetic cell structure of FIG. 15A in a switching configuration,the upper stressor structure and the lower stressor structure configuredto vertically expand during switching.

FIG. 16A is a cross-sectional, elevational, schematic illustration of amagnetic cell structure in a storage configuration, the magnetic cellstructure including an upper stressor structure proximate to a freeregion and a lower stressor structure proximate to a fixed region of anin-plane STT-MRAM cell, the free region and the fixed region formed of amagnetic material having positive magnetostriction.

FIG. 16B is a cross-sectional, elevational, schematic illustration ofthe magnetic cell structure of FIG. 16A in a switching configuration,the upper stressor structure configured to vertically contract duringswitching and the lower stressor structure configured to verticallyexpand during switching.

FIG. 17 is a partial, cross-sectional, elevational, schematicillustration of a magnetic cell structure having a stressor structureformed of multiple stressor sub-regions.

FIG. 18 is a partial, cross-sectional, elevational, schematicillustration of a magnetic cell structure having a discontinuousstressor structure.

FIG. 19 is a partial, cross-sectional, elevational, schematicillustration of a magnetic cell structure having a stressor structureproximate to a magnetic region and an intermediate structure locatedbetween the stressor structure and the magnetic region.

FIG. 20 is a partial, cross-sectional, elevational, schematicillustration of a magnetic cell structure having a heater structureproximate to a stressor structure.

FIG. 21 is a schematic diagram of an STT-MRAM system including a memoryhaving a magnetic cell structure according to an embodiment of thepresent disclosure.

FIG. 22 is a simplified block diagram of a semiconductor devicestructure including memory cells having a magnetic cell structureaccording to an embodiment of the present disclosure.

FIG. 23 is a simplified block diagram of a system implemented accordingto one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Memory cells, semiconductor device structures including such memorycells, memory systems, and methods of forming and operating such memorycells are disclosed. The memory cells include magnetic cell coresincluding a magnetic region, such as a free region or a fixed region,and a stressor structure configured to exert a stress upon the magneticregion during switching to alter a magnetic anisotropy (MA) of themagnetic region during switching. The stress may be a compressive or atensile stress. Programming current passed through the magnetic cellcore during switching (i.e., during programming) may effect a structuralalteration in the stressor structure, such as an expansion orcontraction, which may cause a compressive or tensile stress to beexerted upon the nearby magnetic region. The resulting strain in themagnetic region may alter the magnetic anisotropy of the magneticregion. For example, the stressor structure may be configured to expand(e.g., laterally, vertically, or both) when heated, and passing theprogramming current through the magnetic cell core may heat the stressorstructure. Expansion of the stressor structure, during programming, maystress a nearby free region (e.g., with a compressive or tensilestress). The free region may be formed of a magnetic material configuredto decrease in magnetic anisotropy strength in the direction of theprimary magnetic orientation of the region (i.e., in a horizontaldirection, if the STT-MRAM cell is an in-plane STT-MRAM cell, or in avertical direction, if the STT-MRAM cell is an out-of-plane STT-MRAMcell) when stressed. Therefore, passage of the programming currentthrough the magnetic cell core may heat the stressor structure, whichmay cause the stressor structure to expand, which expansion may causethe free region to be stressed, which stress may result in lowering ofthe MA strength of the free region. Thus, during switching, a lowerprogramming current may be used to switch the magnetic orientation ofthe stressed free region than would be needed were the free region notstressed. For example, the lower programming current may be up to aboutfive times (5×) lower than the programming current that may be needed toswitch the free region if not stressed. (That is, the programmingcurrent needed to switch a non-stressed free region may be up to about500% greater than the programming current needed to switch a stressedfree region.) After switching, the programming current may beterminated, the stressor structure may cool and contract back to itsoriginal dimensions, alleviating the stress on the free region, suchthat the MA strength of the free region may increase back to itsoriginal MA strength. Therefore, the STT-MRAM cell may be configured toenable use of a low programming current without deteriorating dataretention and reliability during storage.

As used herein, the term “substrate” means and includes a base materialor other construction upon which components, such as those within memorycells, are formed. The substrate may be a semiconductor substrate, abase semiconductor material on a supporting structure, a metalelectrode, or a semiconductor substrate having one or more materials,structures, or regions formed thereon. The substrate may be aconventional silicon substrate or other bulk substrate including asemiconductive material. As used herein, the term “bulk substrate” meansand includes not only silicon wafers, but also silicon-on-insulator(“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates orsilicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on abase semiconductor foundation, or other semiconductor or optoelectronicmaterials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, forexample, a mole fraction between 0.2 and 0.8), germanium (Ge), galliumarsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), amongothers. Furthermore, when reference is made to a “substrate” in thefollowing description, previous process stages may have been utilized toform materials, regions, or junctions in the base semiconductorstructure or foundation.

As used herein, the term “STT-MRAM cell” means and includes a magneticcell structure that includes a magnetic cell core including anon-magnetic region disposed between a free region and a fixed region.The non-magnetic region may be an electrically insulative (e.g.,dielectric) region, in a magnetic tunnel junction (“MTJ”) configuration.Alternatively, the non-magnetic region may be an electrically conductiveregion, in a spin-valve configuration.

As used herein, the term “magnetic cell core” means and includes amemory cell structure comprising the free region and the fixed regionand through which, during use and operation of the memory cell, currentmay be passed (i.e., flowed) to effect a parallel or anti-parallelconfiguration of the magnetic orientations of the free region and thefixed region.

As used herein, the term “magnetic region” means a region that exhibitsmagnetism. A magnetic region includes a magnetic material and may alsoinclude one or more non-magnetic materials.

As used herein, the term “magnetic material” means and includes bothferromagnetic materials, ferrimagnetic materials, and antiferromagneticmaterials.

As used herein, the term “fixed region” means and includes a magneticregion within the STT-MRAM cell that includes a magnetic material andthat has a fixed magnetic orientation during use and operation of theSTT-MRAM cell in that a current or applied field effecting a change inthe magnetization direction of one magnetic region, e.g., the freeregion, of the cell core may not effect a change in the magnetizationdirection of the fixed region. The fixed region may include one or moremagnetic materials and, optionally, one or more non-magnetic materials.For example, the fixed region may be configured as a syntheticantiferromagnet (SAF) including a sub-region of ruthenium (Ru) adjoinedby magnetic sub-regions. Each of the magnetic sub-regions may includeone or more materials and one or more regions therein. As anotherexample, the fixed region may be configured as a single, homogeneousmagnetic material. Accordingly, the fixed region may have uniformmagnetization, or sub-regions of differing magnetization that, overall,effect the fixed region having a fixed magnetic orientation during useand operation of the STT-MRAM cell.

As used herein, the term “free region” means and includes a magneticregion within the STT-MRAM cell that includes a magnetic material andthat has a switchable magnetic orientation during use and operation ofthe STT-MRAM cell. The magnetic orientation may be switched between aparallel configuration and an anti-parallel configuration by theapplication of a current or applied field.

As used herein, “switching” means and includes a stage of use andoperation of the memory cell during which programming current is passedthrough the magnetic cell core of the STT-MRAM cell to effect a parallelor anti-parallel configuration of the magnetic orientations of the freeregion and the fixed region.

As used herein, “storage” means and includes a stage of use andoperation of the memory cell during which programming current is notpassed through the magnetic cell core of the STT-MRAM cell and in whichthe parallel or anti-parallel configuration of the magnetic orientationsof the free region and the fixed region is not altered.

As used herein, the terms “expand” and “expansion,” when used inreference to a material's change in size, means and includes thematerial increasing in size, along an axis, more than a neighboringmaterial increases in size along the axis. The terms also refer to amaterial increasing in size, along an axis, while a neighboring materialdoes not change in size or decreases in size along the axis. Thereferenced “neighboring material” is a material that is adjacent to theexpanding material along the same axis on which the expanding materialincreases in size. The end result of the change in size is that theratio of the size of the material to the neighboring material after theexpansion is greater than the ratio of the size of the material to theneighboring material before the expansion. Thus, a material that triplesin length or height may be said to “expand” if a neighboring materialmerely doubles in length or height. Additionally, a material thatincreases in size while a neighboring material does not change in sizeor reduces in size may also be said to “expand.” In the context of“lateral expansion,” the referenced neighboring material is a materiallaterally adjacent to the expanding material. Thus, a laterally expandedmaterial may be “expanded” relative to the laterally-adjacent materialand may exert a lateral compressive stress upon such neighboringmaterial. The laterally-expanded material may also exert a lateraltensile stress upon vertically adjacent materials, which lateral tensilestress may effect a lateral expansion of the vertically-adjacentmaterials. In the context of “vertical expansion,” the referencedneighboring material is a material vertically adjacent to the expandingmaterial. Thus, a vertically expanded material may be “expanded”relative to the vertically-adjacent material and may exert a verticalcompressive stress upon such neighboring material. Thevertically-expanded material may also exert a vertical tensile stressupon laterally adjacent materials, which vertical tensile stress mayeffect a vertical expansion of the laterally-adjacent materials.

As used herein, the terms “contract” and “contraction,” when used inreference to a material's change in size, means and includes thematerial decreasing in size, along an axis, more than a neighboringmaterial decreases in size along the axis. The terms also refer to amaterial decreasing in size, along an axis, while a neighboring materialdoes not change in size or increases in size along the axis. Thereferenced “neighboring material” is a material that is adjacent to thecontracting material along the same axis on which the contractingmaterial decreases in size. The end result of the change in size is thatthe ratio of the size of the material to the neighboring material afterthe contraction is less than the ratio of the size of the material tothe neighboring material before the contraction. Thus, a material thatshrinks in size while a neighboring material expands or does not changein size may be said to “contract.” Moreover, a material that shrinks insize more than a neighboring material shrinks in size may be said to“contract.” Additionally, however, a material that doubles in length orheight may be said to “contract” if a neighboring material triples inlength or height. In the context of “lateral contraction,” thereferenced neighboring material is a material laterally adjacent to thecontracting material. Thus, a laterally contracted material may be“contracted” relative to the laterally-adjacent material and may exert alateral tensile stress upon such neighboring material. Thelaterally-contracted material may also exert a lateral compressivestress upon vertically adjacent materials, which lateral compressivestress may effect a lateral contraction of the vertically-adjacentmaterials. In the context of “vertical contraction,” the referencedneighboring material is a material vertically adjacent to thecontracting material. Thus, a vertically contracted material may be“contracted” relative to the vertically-adjacent material and may exerta vertical tensile stress upon such neighboring material. Thevertically-contracted material may also exert a vertical compressivestress upon laterally adjacent material, which vertical compressivestress may effect a vertical contraction of the laterally-adjacentmaterials.

As used herein, the term “vertical” means and includes a direction thatis perpendicular to the width and length of the respective region.“Vertical” may also mean and include a direction that is perpendicularto a primary surface of the substrate on which the STT-MRAM cell islocated.

As used herein, the term “horizontal” means and includes a directionthat is parallel to at least one of the width and length of therespective region. “Horizontal” may also mean and include a directionthat is parallel to a primary surface of the substrate on which theSTT-MRAM cell is located.

As used herein, the term “sub-region” means and includes a regionincluded in another region. Thus, one magnetic region may include one ormore magnetic sub-regions, i.e., sub-regions of magnetic material, aswell as non-magnetic sub-regions, i.e., sub-regions of non-magneticmaterial.

As used herein, the term “between” is a spatially relative term used todescribe the relative disposition of one material, region, or sub-regionrelative to at least two other materials, regions, or sub-regions. Theterm “between” can encompass both a disposition of one material, region,or sub-region directly adjacent to the other materials, regions, orsub-regions and a disposition of one material, region, or sub-region notdirectly adjacent to the other materials, regions, or sub-regions.

As used herein, reference to an element as being “on” or “over” anotherelement means and includes the element being directly on top of,adjacent to, underneath, or in direct contact with the other element. Italso includes the element being indirectly on top of, adjacent to,underneath, or near the other element, with other elements presenttherebetween. In contrast, when an element is referred to as being“directly on” or “directly adjacent to” another element, there are nointervening elements present.

As used herein, other spatially relative terms, such as “beneath,”“below,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,”“left,” “right,” and the like, may be used for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the figures. Unless otherwise specified,the spatially relative terms are intended to encompass differentorientations of the materials in addition to the orientation as depictedin the figures. For example, if materials in the figures are inverted,elements described as “below” or “beneath” or “under” or “on bottom of”other elements or features would then be oriented “above” or “on top of”the other elements or features. Thus, the term “below” can encompassboth an orientation of above and below, depending on the context inwhich the term is used, which will be evident to one of ordinary skillin the art. The materials may be otherwise oriented (rotated 90 degrees,inverted, etc.) and the spatially relative descriptors used hereininterpreted accordingly.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or“including” specify the presence of stated features, regions, integers,stages, operations, elements, materials, components, and/or groups, butdo not preclude the presence or addition of one or more other features,regions, integers, stages, operations, elements, materials, components,and/or groups thereof.

As used herein, “and/or” includes any and all combinations of one ormore of the associated listed items.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

The illustrations presented herein are not meant to be actual views ofany particular component, structure, device, or system, but are merelyidealized representations that are employed to describe embodiments ofthe present disclosure.

Embodiments are described herein with reference to cross-sectionalillustrations that are schematic illustrations. Accordingly, variationsfrom the shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments described herein are not to be construed as limited to theparticular shapes or regions as illustrated but may include deviationsin shapes that result, for example, from manufacturing techniques. Forexample, a region illustrated or described as box-shaped may have roughand/or nonlinear features. Moreover, sharp angles that are illustratedmay be rounded. Thus, the materials, features, and regions illustratedin the figures are schematic in nature and their shapes are not intendedto illustrate the precise shape of a material, feature, or region and donot limit the scope of the present claims.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the disclosed devices and methods.However, a person of ordinary skill in the art will understand that theembodiments of the devices and methods may be practiced withoutemploying these specific details. Indeed, the embodiments of the devicesand methods may be practiced in conjunction with conventionalsemiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a completeprocess flow for processing semiconductor device structures. Theremainder of the process flow is known to those of ordinary skill in theart. Accordingly, only the methods and semiconductor device structuresnecessary to understand embodiments of the present devices and methodsare described herein.

Unless the context indicates otherwise, the materials described hereinmay be formed by any suitable technique including, but not limited to,spin coating, blanket coating, chemical vapor deposition (“CVD”), atomiclayer deposition (“ALD”), plasma enhanced ALD, or physical vapordeposition (“PVD”). Alternatively, the materials may be grown in situ.Depending on the specific material to be formed, the technique fordepositing or growing the material may be selected by a person ofordinary skill in the art.

Unless the context indicates otherwise, the removal of materialsdescribed herein may be accomplished by any suitable techniqueincluding, but not limited to, etching, ion milling, abrasiveplanarization, or other known methods.

Reference will now be made to the drawings, where like numerals refer tolike components throughout. The drawings are not necessarily drawn toscale.

A memory cell is disclosed. The memory cell includes a magnetic cellcore that includes at least one magnetic region (e.g., a free region ora fixed region) and a stressor structure proximate to the magneticregion. The stressor structure is configured to exert a stress upon themagnetic region during switching of the memory cell. The stress effectsan alteration in a magnetic anisotropy (“MA”) of the stressed magneticregion during switching. After switching, the stress may be alleviatedand the MA of the magnetic region may revert to substantially itsprevious level. The stressor structure may therefore be configured tocause a decrease in the MA strength of a free region during switching oran increase in the MA strength of a fixed region during switching.

The memory cells of embodiments of the present disclosure may beconfigured as either in-plane STT-MRAM cells or out-of-plane STT-MRAMcells. “In-plane” STT-MRAM cells include magnetic regions exhibiting amagnetic orientation that is predominantly oriented in a horizontaldirection, while “out-of-plane” STT-MRAM cells include magnetic regionsexhibiting a magnetic orientation that is predominantly oriented in avertical direction. As used herein “direction” when referring tomagnetic orientation refers to the predominant direction of the magneticorientation.

FIGS. 1 through 3C illustrate an embodiment of an out-of-plane STT-MRAMcell. With reference to FIG. 1, illustrated is a magnetic cell structure100 of an out-of-plane STT-MRAM cell according to an embodiment of thepresent disclosure. The magnetic cell structure 100 includes a magneticcell core 101 over a substrate 102. The magnetic cell core 101 may bedisposed between an upper electrode 104 above and a lower electrode 105below. The magnetic cell core 101 includes at least two magneticregions, for example, a “fixed region” 110 and a “free region” 120 witha nonmagnetic region 130 in between. One or more lower intermediaryregions 140 and one or more upper intermediary regions 150 may,optionally, be disposed under and over, respectively, the magneticregions (e.g., the fixed region 110 and the free region 120) of themagnetic cell structure 100.

In some embodiments, as illustrated in FIG. 1, the magnetic cell core101 may include an optional conductive material forming a seed region160 over the substrate 102. The seed region 160, if present, or thelower intermediary regions 140, if the seed region 160 is not present,may be formed over a bottom conductive material of a lower electrode105, which may include, for example and without limitation, copper,tungsten, titanium, tantalum, a nitride of any of the foregoing, or acombination thereof. The seed region 160, if present, may include, forexample and without limitation, a nickel-based material and may beconfigured to control the crystal structure of an overlying material orregion. The lower intermediary regions 140, if present, may includematerials configured to ensure a desired crystal structure of overlyingmaterials in the magnetic cell core 101.

The magnetic cell structure 100 may, in some embodiments, optionallyinclude an oxide capping region 170, which may include oxides such asmagnesium oxide (MgO), aluminum oxide (Al₂O₃), titanium oxide (TiO₂),tantalum pentoxide (Ta₂O₅), or combinations thereof. In someembodiments, the oxide capping region 170 may include the samematerials, structure, or both of the nonmagnetic region 130, forexample, the oxide capping region 170 and the nonmagnetic region 130 mayboth include a magnesium oxide (e.g., MgO), an aluminum oxide, atitanium oxide, a zinc oxide, hafnium oxide, a ruthenium oxide, or atantalum oxide. The oxide capping region 170 and the nonmagnetic region130 may include one or more nonmagnetic materials.

The optional upper intermediary regions 150, if present, may includematerials configured to ensure a desired crystal structure inneighboring materials of the magnetic cell core 101. The upperintermediary regions 150 may alternatively or additionally include metalmaterials configured to aid in patterning processes during fabricationof the magnetic cell core 101, barrier materials, or other materials ofconventional STT-MRAM cell core structures. In some embodiments, such asthat illustrated in FIG. 1, the upper intermediary regions 150 mayinclude a conductive capping region, which may include one or morematerials such as copper, tantalum, titanium, tungsten, ruthenium,tantalum nitride, or titanium nitride.

As illustrated in FIG. 1, the STT-MRAM cell may be configured to exhibita vertical magnetic orientation in at least one of the magnetic regions(e.g., the fixed region 110 and the free region 120). The verticalmagnetic orientation exhibited may be characterized by the perpendicularmagnetic anisotropy (“PMA”) strength. As illustrated in FIG. 1 by arrows112 and double-pointed arrows 122, in some embodiments, each of thefixed region 110 and the free region 120 may exhibit a vertical magneticorientation. The magnetic orientation of the fixed region 110 may remaindirected in essentially the same direction throughout operation of theSTT-MRAM cell, for example, in the direction indicated by arrows 112 ofFIG. 1. The magnetic orientation of the free region 120, on the otherhand, may be switched, during operation of the cell, between a parallelconfiguration and an anti-parallel configuration, as indicated bydouble-pointed arrows 122 of FIG. 1.

The magnetic cell core 101 also includes a stressor structure 180proximate to at least one of the free region 120 and the fixed region110. As illustrated in the embodiment of FIG. 1, the stressor structure180 may be proximate to the free region 120. The stressor structure 180may be formed of a material, e.g., a nonmagnetic material, configured tochange shape, in at least one dimension (e.g., height, width), duringprogramming of the STT-MRAM cell. One or more of the structuralconfiguration, the location, and material composition of the stressorstructure 180 may be tailored to enable the stressor structure 180 toalter in shape during programming to apply a desired magnitude anddirection of stress upon a neighboring region. As used herein, the term“configured,” when referring to the stressor structure 180, means andincludes a stressor structure 180 having at least one of its structuralconfiguration, its location (e.g., relative to the magnetic materialbeing impacted), and material composition tailored so as to enable theresult for which the stressor structure 180 is described to be“configured.”

The stressor structure 180 may be configured to expand or contract(i.e., to reduce in dimension or to expand less than a neighboringmaterial) during programming in response to a change in a conditionduring programming, such as an increase in temperature or a drop involtage. For example, passing a programming current through the magneticcell core 101, including the stressor structure 180, during switching ofthe STT-MRAM cell may heat the material of the stressor structure 180and other materials within the magnetic cell core 101. Therefore, duringprogramming, the dimensions of the stressor structure 180, if configuredto respond to a temperature change, may be altered, causing a physicalstress to be exerted by the altered stressor structure 180 upon theneighboring magnetic material. The stress may be alleviated when theprogramming current is halted, causing the temperature to return to apre-switching level and the stressor structure 180 to return to itspre-switching dimensions.

In embodiments in which the stressor structure 180 is configured torespond to a temperature change, the stressor structure 180 may beformed of a material having a coefficient of thermal expansion that isdifferent than (e.g., at least about 0.1% greater than or at least about0.1% less than) a coefficient of thermal expansion of a neighboringmaterial, e.g., a neighboring magnetic material of a neighboringmagnetic region. As such, the stressor structure 180 may be configuredto expand or contract at a different rate, when exposed to a temperaturechange, than a neighboring material, e.g., a neighboring magneticmaterial. For example, and without limitation, the stressor structure180 may be formed of or comprise a metal (e.g., aluminum (Al), copper(Cu)) or other material (e.g., silicon (Si), germanium (Ge)) having ahigher coefficient of thermal expansion (e.g., compared to thecoefficient of thermal expansion of at least the material of themagnetic region to be stressed by the stressor structure 180), and may,thus, be configured to expand more than a neighboring material, whensubjected to a programming current during switching that heats thestressor structure 180, and exert a stress upon a neighboring magneticregion. In other embodiments, the stressor structure 180 may beconfigured to reduce in volume, when subjected to a programming currentduring switching that heats the stressor structure 180, and exert astress upon a neighboring magnetic region. Such stressor structure 180may be formed of a material having a negative coefficient of thermalexpansion. Alternatively, the stressor structure 180 may be formed of orcomprise a material having a lower coefficient of thermal expansion thana neighboring material, such that, when the materials of the magneticcell core 101 are subjected to a programming current during switchingthat heats the materials, the stressor structure 180 may expand lessthan the neighboring material. Thus, the stressor structure 180 maycontract relative to the neighboring material.

In embodiments in which the stressor structure 180 is configured torespond to a voltage change, the stressor structure 180 may be formed ofa piezoelectric material that changes shape (e.g., expands or contracts,relative to a neighboring material) in response to a change in voltageacross its thickness during programming.

Depending on the materials neighboring the stressor structure 180 withinthe magnetic cell core 101 or external to the magnetic cell core 101,the stressor structure 180 may be configured to alter a dimensionprimarily in one direction. For example, the stressor structure 180 maybe configured to vertically expand, to vertically contract, to laterallyexpand, or to laterally contract when exposed to the conditions of theswitching stage. Thus, it is contemplated that the materials andstructural configuration of the stressor structure 180 may be tailoredto accomplish a desired dimensional alteration and its correspondingstress exertion upon the neighboring magnetic region. The material ofthe stressor structure 180 may also be formulated to be inert (e.g., tonot chemically react) with neighboring materials at processingtemperatures.

The free region 120 and the fixed region 110 may be formed from orcomprise a magnetic material 220 (see FIG. 2A) having positivemagnetostriction or a magnetic material 320 (see FIG. 3A) havingnegative magnetostriction. As used herein, “magnetostriction” refers toa property of a magnetic material that causes the material to change itsshape or dimensions during the process of magnetization. A magneticmaterial 220 having “positive magnetostriction” tends to elongate in thedirection of its magnetization (i.e., in the direction of its magneticorientation), while a magnetic material 320 having “negativemagnetostriction” tends to contract in the direction of itsmagnetization. An MA strength in the direction of predominant magneticorientation of a magnetic material 220 with positive magnetostrictionmay increase when the magnetic material 220 is expanded (e.g., pulled)in the direction of its magnetic orientation but may decrease when themagnetic material 220 is compressed (e.g., pushed) against the directionof its magnetic orientation. An MA strength in the direction ofpredominant magnetic orientation of a magnetic material 320 withnegative magnetostriction may decrease when the magnetic material 320 isexpanded (e.g., pulled) in the direction of its magnetic orientation butmay increase when the magnetic material 320 is compressed (e.g., pushed)against the direction of its magnetic orientation. Thus, according toembodiments of the present disclosure, at least one of the free region120 and the fixed region 110 may be configured to be expanded orcompressed, along its direction of predominant magnetic orientation,during switching to effect an alteration to the MA strength in theexpanded or contracted region during switching. The physical expansionor physical compression may result from a stress exerted on the magneticregion by the stressor structure 180 as it is altered duringprogramming, as discussed above.

One or both of the magnetic regions (e.g., the fixed region 110 and thefree region 120) of the magnetic cell core 101 may comprise, consistessentially of, or consist of magnetic material exhibiting eitherpositive or negative magnetostriction. Magnetic material 220 exhibitingpositive magnetostriction may include, for example and withoutlimitation, ferromagnetic material including cobalt (Co) and iron (Fe)(e.g., CoFe, CoFeB) with a cobalt to iron (Co:Fe) ratio of less than9:1. Magnetic material 320 exhibiting negative magnetostriction mayinclude, for example and without limitation, ferromagnetic materialincluding cobalt (Co) and iron (Fe) (e.g., CoFe, CoFeB) with a cobalt toiron (Co:Fe) ratio of greater than 9:1. Other magnetic materials thatmay, optionally, be included in the fixed region 110, the free region120, or both include, for example and without limitation, Co, Fe, Ni ortheir alloys, NiFe, CoNiFe, or doped alloys CoX, CoFeX, CoNiFeX (X=B,Cu, Re, Ru, Rh, Hf, Pd, Pt, C), or other half-metallic ferromagneticmaterials, such as, for example, NiMnSb and PtMnSb.

In some embodiments, magnetic regions (e.g., the fixed region 110 andthe free region 120) include both magnetic materials exhibitingmagnetostriction and magnetic materials not exhibiting magnetostriction.Nonetheless, the MA strength of the magnetic region may decrease orincrease when the magnetic region is stressed.

Alternatively or additionally, in some embodiments, the free region 120,the fixed region 110, or both, may be formed from or comprise aplurality of materials, some of which may be magnetic materials (e.g.,magnetic materials exhibiting magnetostriction and magnetic materialsnot exhibiting magnetostriction) and some of which may be nonmagneticmaterials. For example, some such multi-material free regions, fixedregions, or both, may include multiple sub-regions. For example, andwithout limitation, the free region 120, the fixed region 110, or both,may be formed from or comprise repeating sub-regions of cobalt andplatinum, wherein a sub-region of platinum may be disposed betweensub-regions of cobalt. As another example, without limitation, the freeregion 120, the fixed region 110, or both, may comprise repeatingsub-regions of cobalt and nickel, wherein a sub-region of nickel may bedisposed between sub-regions of cobalt.

The compositions and structures (e.g., the thicknesses and otherphysical dimensions) of the free region 120 and the fixed region 110 maybe the same or different.

With reference to FIG. 2A, illustrated is a free region 120 of themagnetic cell structure 100 of FIG. 1, wherein the free region 120 isformed of the magnetic material 220 having positive magnetostriction.FIG. 2A illustrates the stressor structure 180 and the free region 120during a storage state in which a programming current is not beingpassed through the magnetic cell core 101 (FIG. 1). The free region 120,in such “storage configuration” exhibits a vertical magnetic orientationhaving a perpendicular magnetic anisotropy with a certain magnitude,represented by arrow PMA.

In some embodiments, the stressor structure 180 is configured tovertically expand under the conditions of a switching stage, e.g., whena programming current is passed through the magnetic cell core 101(FIG. 1) and heats the stressor structure 180. In such embodiments, asillustrated in FIG. 2B, expansion in the direction indicated by arrowV_(E) creates a vertically expanded stressor structure 180 _(VE) thatexerts a vertical compressive force on the neighboring magnetic material220. A resulting vertically compressed free region 120 _(VC) may exhibita lowered PMA, as indicated by the lesser magnitude of arrow PMA_(L)compared to the magnitude of arrow PMA of FIG. 2A. Thus, duringswitching, the programming current results in the vertically expandedstressor structure 180 _(VE), the vertically compressed free region 120_(VC), and the lowered PMA_(L). The lowered PMA_(L) may enable switchingof the magnetic orientation of the vertically compressed free region 120_(VC) at a lower programming current than would otherwise be utilized.

Following switching, the application of the programming current may bestopped, which may result in a return to pre-switching conditions,including temperature, during which the vertically expanded stressorstructure 180 _(VE) may return to the storage configuration illustratedin FIG. 2A, alleviating the stress previously exerted to form thevertically compressed free region 120 _(VC). Thus, the verticallycompressed free region 120 _(VC) may expand to its storage configurationillustrated in FIG. 2A, and the lowered PMA_(L) may increase to the PMAof the free region 120 in FIG. 2A. Therefore, the lowered PMA_(L) may beexhibited by the vertically compressed free region 120 _(VC) duringswitching, while the original PMA may be exhibited by the free region120 during storage. Accordingly, the free region 120 may enableswitching at a lower programming current without deteriorating dataretention during storage.

Differentiating between the PMA strength during switching and duringstorage may accommodate scalability of the magnetic cell structures 100.For example, enabling the fixed region 110 to be switched at a lowerprogramming current, without deteriorating the PMA strength of the fixedregion 110 during storage may enable fabrication of a smaller fixedregion 110 without deteriorating the functionality of the fixed region110.

In other embodiments, the stressor structure 180 (FIG. 2A) may beconfigured to laterally expand under the conditions of a switchingstage, e.g., when a programming current is passed through the magneticcell core 101 (FIG. 1) and heats the stressor structure 180. In suchembodiments, as illustrated in FIG. 2C, expansion in the directionindicated by arrow L_(E) creates a laterally expanded stressor structure180 _(LE) that exerts a lateral tensile force on the neighboringmagnetic material 220. A resulting laterally expanded free region 120_(LE) may exhibit a lowered PMA, as indicated by the lesser magnitude ofarrow PMA_(L) compared to the magnitude of arrow PMA of FIG. 2A. Thus,during switching, the programming current results in the laterallyexpanded stressor structure 180 _(LE), the laterally expanded freeregion 120 _(LE), and the lowered PMA_(L). The lowered PMA_(L) mayenable switching of the magnetic orientation of the laterally expandedfree region 120 _(LE) at a lower programming current than wouldotherwise be required.

With reference to FIGS. 3A through 3C, illustrated is a free region 120of the magnetic cell structure 100 of FIG. 1, wherein the free region120 is formed of the magnetic material 320 having negativemagnetostriction. In some embodiments, the stressor structure 180 may beconfigured to vertically contract, as indicated by arrow V_(C),resulting in a vertically contracted stressor structure 180 _(VC) thatexerts a vertical tensile stress upon the free region 120, resulting ina vertically expanded free region 120 _(VE). The magnetic material 320of the vertically expanded free region 120 _(VE) may exhibit a loweredPMA_(L). Therefore, the magnetic orientation of the vertically expandedfree region 120 _(VE) may be switchable at a low programming current.

With reference to FIG. 3C, in other embodiments, the stressor structure180 may be configured to laterally contract, as indicated by arrowL_(C), resulting in a laterally contracted stressor structure 180 _(LC)that exerts a lateral compressive stress upon the free region 120,resulting in a laterally compressed free region 120 _(LC). The magneticmaterial 320 of the laterally compressed free region 120 _(LC) mayexhibit a lowered PMA_(L) with a magnetic orientation that may beswitchable at a low programming current.

With reference to FIG. 4, illustrated is a magnetic cell structure 400of an in-plane STT-MRAM cell in which the magnetic material of the fixedregion 110 and the free region 120 in the magnetic cell core 401 exhibithorizontal magnetic orientation, as indicated by arrows 412 anddouble-pointed arrows 422.

With reference to FIG. 5A, in some embodiments, the free region 120 ofthe in-plane STT-MRAM cell may be formed of the magnetic material 320exhibiting negative magnetostriction. The horizontal magneticorientation exhibited by the magnetic material 320 may be characterizedby the in-plane magnetic anisotropy (“IMA”) strength. In someembodiments, the stressor structure 180 may be configured to verticallyexpand, in the direction of arrow V_(E) of FIG. 5B, during switching,resulting in a vertically expanded stressor structure 180 _(VE) thatexerts a vertical compressive stress upon the neighboring magneticmaterial 320, which results in vertically compressed free region 120_(VC). The vertically compressed free region 120 _(VC) may, therefore,exhibit a lowered IMA_(L) such that the magnetic orientation of thevertically compressed free region 120 _(VC) may be switchable at a lowprogramming current. After switching, the vertically expanded stressorstructure 180 _(VE) and the vertically compressed free region 120 _(VC)may return to the configuration illustrated in FIG. 5A.

With reference to FIG. 5C, in some embodiments, the stressor structure180 may be configured to laterally expand, in the direction of arrowL_(E), during switching, resulting in a laterally expanded stressorstructure 180 _(LE) that exerts a lateral tensile stress upon themagnetic material 320, producing laterally expanded free region 120_(LE). The laterally expanded free region 120 _(LE) may, therefore,exhibit a lowered IMA_(L) such that the magnetic orientation of thelaterally expanded free region 120 _(LE) may be switchable at a lowprogramming current. After switching, the laterally expanded stressorstructure 180 _(LE) and the laterally expanded free region 120 _(LE) mayreturn to the configuration illustrated in FIG. 5A.

In other embodiments, the free region 120 (FIG. 4) of the magnetic cellcore 401 of the in-plane STT-MRAM memory cell may be formed from themagnetic material 220 exhibiting positive magnetostriction, asillustrated in FIG. 6A. Thus, with reference to FIG. 6B, the stressorstructure 180 may be configured to vertically contract during switchingto exert a vertical tensile stress upon the free region 120, resultingin the vertically contracted stressor structure 180 _(VC), thevertically expanded free region 120 _(VE), and the lowered IMA_(L). Withreference to FIG. 6C, the stressor structure 180 may alternatively oradditionally be configured to laterally contract during switching toexert a lateral compressive stress upon the free region 120, resultingin the laterally contracted stressor structure 180 _(LC), the laterallycompressed free region 120 _(LC), and the lowered IMA_(L). Afterswitching, the regions and structures may return to the configurationillustrated in FIG. 6A.

Accordingly, disclosed is a memory cell comprising a magnetic cell corecomprising a magnetic region and a stressor structure. The stressorstructure is configured to exert a stress upon the magnetic region andto alter a magnetic anisotropy of the magnetic region when the stressorstructure is subjected to a programming current passing through themagnetic cell core during switching of a magnetic orientation of themagnetic region.

Because the magnetic material 220 exhibiting positive magnetostrictionreacts differently to vertical and lateral compressive and tensilestress produced by a neighboring stressor structure 180, it iscontemplated that the stressor structure 180 be configured and orientedto exert the appropriate stress (e.g., vertical compressive (as in FIG.2B), lateral tensile (as in FIG. 2C), vertical tensile (as in FIG. 3B),and lateral compressive (as in FIG. 3C)) to effect an increase in the MAstrength of the magnetic material (e.g., the magnetic material 220exhibiting positive magnetostriction, the magnetic material 320exhibiting negative magnetostriction). In embodiments in which themagnetic region to be impacted by the stressor structure 180 is the freeregion 120, it is contemplated that the stressor structure 180 beconfigured to exert a stress that results in a lowering of the MAstrength of the magnetic orientation exhibited by the free region 120.

Regardless of whether the STT-MRAM cell is configured as an out-of-planecell (as in FIGS. 1 through 3C) or an in-plane cell (as in FIGS. 4through 6C), whether the magnetic material of the magnetic region (e.g.,the free region 120) is formed of the magnetic material 220 exhibitingpositive magnetostriction or the magnetic material 320 exhibitingnegative magnetostriction, and whether the stressor structure 180 isconfigured to vertically expand, vertically contract, laterally expand,or laterally contract, passing a programming current through themagnetic cell core (e.g., the magnetic cell core 101 (FIG. 1), themagnetic cell core 401 (FIG. 4)), during a switching stage, alters amagnetic orientation of the free region 120 and, therefore, alters anelectrical resistance across the free region 120 and the fixed region110 of the magnetic cell core (e.g., the magnetic cell core 101 (FIG.1), the magnetic cell core 401 (FIG. 4)). Moreover, the alteration in atleast one dimension of the stressor structure 180 is accomplished whilethe current is being passed through the magnetic cell core, and thealteration in the stressor structure 180 exerts the stress upon theneighboring magnetic region (e.g., the free region 120 or the fixedregion 110) to alter the MA strength of the magnetic region.

Accordingly, disclosed is a method of operating a spin torque transfermagnetic random access memory (STT-MRAM) cell. The method comprisesaltering an electrical resistance across a magnetic region and anothermagnetic region of a magnetic cell core of the STT-MRAM cell to programa logic stage of the STT-MRAM cell. Altering the electrical resistancecomprises passing a current through the magnetic cell core to switch aswitchable magnetic orientation of the magnetic region. Responsive atleast in part to passing the current, at least one dimension of astressor structure, proximate to one of the magnetic region and theanother magnetic region, is altered to exert a stress upon the one ofthe magnetic region and the another magnetic region and to alter amagnetic anisotropy of the one of the magnetic region and the anothermagnetic region.

With reference to FIG. 7, in some embodiments, a magnetic cell structure700 may include a magnetic cell core 701 that includes an upper stressorstructure 781 proximate to the free region 120 and a lower stressorstructure 782 proximate to the fixed region 110. The upper stressorstructure 781 may be configured like any of the stressor structures 180described above with respect to FIGS. 1 through 3C. Thus, the upperstressor structure 781 may be configured to exert a stress upon the freeregion 120 during switching to lower the MA strength of the free region120 during switching, enabling a lower programming current to be usedduring switching.

The lower stressor structure 782 may be disposed proximate to the fixedregion 110 and may be configured to exert a stress upon the fixed region110 during switching so as to alter an MA strength of the fixed region110 during switching. It is contemplated that the lower stressorstructure 782 may be configured to exert a stress that results in ahigher (e.g., greater) MA strength in the fixed region 110. The higherMA strength may enable switching of the magnetic orientation of the freeregion 120, because the MA strength of the fixed region 110 may enhancethe torque created as the programming current passes through themagnetic cell core 701.

The lower stressor structure 782 may also inhibit a decrease in magneticanisotropy of the fixed region 110 during programming. For example, ifthe magnetic material of the fixed region 110 is apt to lower in MAstrength when exposed to a temperature increase, then the stress exertedupon the fixed region 110 by the lower stressor structure 782 mayinhibit the MA strength lowering.

With reference to FIG. 8A, in some embodiments, the fixed region 110 maybe formed of the magnetic material 220 exhibiting positivemagnetostriction and may exhibit a vertical magnetic orientationcharacterized by a PMA strength indicated by the magnitude of arrow PMAin FIG. 8A. So as to increase the PMA strength during switching, thelower stressor structure 782 may be configured to vertically contract,as indicated by arrow V_(C) of FIG. 8B, during switching, which verticalcontraction may exert a vertical tensile stress upon the magneticmaterial 220 exhibiting positive magnetostriction and so increase thePMA strength of the magnetic material 220. Therefore, during switching,the programming current may result in a vertically contracted stressorstructure 782 _(VC), a vertically expanded fixed region 110 _(VE), and ahigher PMA_(H). After switching, the structure may return to the storageconfiguration illustrated in FIG. 8A.

Alternatively or additionally, the lower stressor structure 782 may beconfigured to laterally contract, in the direction of arrow L_(C) ofFIG. 8C. Lateral contraction results in a laterally contracted stressorstructure 782 _(LC) that exerts a lateral compressive stress upon thefixed region 110, resulting in a laterally compressed fixed region 110_(LC) that exhibits a higher PMA_(H). After switching, the structure mayreturn to the configuration illustrated in FIG. 8A.

With reference to FIG. 9A, in some embodiments, the fixed region 110 maybe formed of the magnetic material 320 exhibiting negativemagnetostriction. Thus, the lower stressor structure 782 may beconfigured to vertically expand, in the direction of arrow V_(E) of FIG.9B, to exert a vertical compressive stress on the magnetic material 320,resulting in a vertically compressed fixed region 110 _(VC) exhibiting ahigher PMA_(H). In other embodiments, the lower stressor structure 782may be configured to laterally expand, in the direction of arrow L_(E)of FIG. 9C, to exert a lateral tensile stress on the magnetic material320, resulting in a laterally expanded fixed region 110 _(LE) exhibitinga higher PMA_(H).

In some embodiments, both the fixed region 110 and the free region 120may be formed of the magnetic material 220 exhibiting the positivemagnetostriction. In such embodiments, the upper stressor structure 781and the lower stressor structure 782 may be configured to oppositelychange in at least one dimension during switching so as to lower the MAstrength of the free region 120 and to increase the MA strength of thefixed region 110. For example, with reference to FIGS. 10A and 10B, amagnetic cell structure 1000A of an out-of-plane STT-MRAM cell mayinclude a magnetic cell core 1001 having two magnetic regions formed ofthe magnetic material 220 exhibiting positive magnetostriction. FIG. 10Aillustrates the magnetic cell structure 1000A in a storageconfiguration. The upper stressor structure 781 may be configured tovertically expand, compressing the free region 120, while the lowerstressor structure 782 may be configured to vertically contract,expanding the fixed region 110. Thus, as illustrated in FIG. 10B, theresulting vertically compressed free region 120 _(VC) may exhibit alowered PMA_(L), while the vertically expanded fixed region 110 _(VE)may exhibit a higher PMA_(H), in magnetic cell structure 1000B, comparedto the PMA strengths of the respective regions of the magnetic cellstructure 1000A of FIG. 10A.

In other embodiments, both the upper stressor structure 781 and thelower stressor structure 782 may be configured to alter in the samedimension, and the fixed region 110 and the free region 120 may beformed of oppositely magnetostrictive materials. For example, withreference to FIGS. 11A and 11B, a magnetic cell structure 1100A of anout-of-plane STT-MRAM cell may include a magnetic cell core 1101 havinga free region 120 formed from the magnetic material 220 exhibitingpositive magnetostriction and fixed region 110 formed of the magneticmaterial 320 exhibiting negative magnetostriction. Both the upperstressor structure 781 and the lower stressor structure 782 may beconfigured to vertically expand, contracting the free region 120 and thefixed region 110. Thus, as illustrated in FIG. 11B, the resultingvertically compressed free region 120 _(VC) may exhibit the loweredPMA_(L), while the vertically compressed fixed region 110 _(VC) mayexhibit a higher PMA_(H), in magnetic cell structure 1100B, compared tothe PMA strength of the respective regions of the magnetic cellstructure 1100A of FIG. 11A. In such embodiments, the upper stressorstructure 781 and the lower stressor structure 782 may be formed fromthe same material.

More than one stressor structure (e.g., an upper stressor structure 781and a lower stressor structure 782) may also be included in embodimentsin which the STT-MRAM cell is configured as an in-plane cell. Withreference to FIG. 12, for example, a magnetic cell structure 1200 mayinclude a magnetic cell core 1201 having an upper stressor structure 781proximate to the free region 120 and a lower stressor structure 782proximate to a fixed region 110. The upper stressor structure 781 may beconfigured like any of the stressor structures 180 described above withrespect to FIGS. 4 through 6C.

In some embodiments, the fixed region 110 may be formed of the magneticmaterial 320 exhibiting negative magnetostriction, as illustrated inFIG. 13A. Therefore, the lower stressor structure 782 may be configuredto vertically contract, in the direction of arrow V_(C) of FIG. 13B, toexert a vertical tensile stress upon the fixed region 110, resulting ina vertically expanded fixed region 110 _(VE) having a higher IMA_(H)compared to the structure of FIG. 13A. Alternatively or additionally,the lower stressor structure 782 may be configured to laterallycontract, in the direction of arrow L_(C) of FIG. 13C, to exert alateral compressive stress upon the fixed region 110, resulting in alaterally compressed free region 110 _(LC) having a higher IMA_(H)compared to the structure of FIG. 13A.

In other embodiments, the fixed region 110 may be formed of the magneticmaterial 220 exhibiting positive magnetostriction, as illustrated inFIG. 14A. Therefore, the lower stressor structure 782 may be configuredto vertically expand, in the direction of arrow V_(E) of FIG. 14B, toexert a vertical compressive stress upon the fixed region 110, resultingin a vertically compressed fixed region 110 _(VC) having a higherIMA_(H) compared to the structure of FIG. 14A. Alternatively oradditionally, the lower stressor structure 782 may be configured tolaterally expand, in the direction of arrow L_(E) of FIG. 14C, and theresulting laterally expanded stressor structure 782 _(LE) may exert alateral tensile stress upon the fixed region 110, resulting in alaterally expanded fixed region 110 _(LE) having a higher IMA_(H)compared to the structure of 14A.

In some embodiments, both the upper stressor structure 781 and the lowerstressor structure 782 may be configured to vertically expand duringswitching while the free region 120 and the fixed region 110 may beformed of magnetic materials exhibiting opposite magnetostriction. Forexample, as illustrated in FIGS. 15A and 15B, a magnetic cell structure1500A of an in-plane STT-MRAM cell may include a magnetic cell core 1501having a free region 120 formed of the magnetic material 320 exhibitingnegative magnetostriction and a fixed region 110 formed of the magneticmaterial 220 exhibiting positive magnetostriction while both the upperstressor structure 781 and the lower stressor structure 782 may beconfigured to vertically expand in the direction of arrows V_(E) of FIG.15B. Therefore, during switching, the resulting vertically expandedstressor structure 781 _(VE) and the vertically expanded stressorstructure 782 _(VE) exert vertical compressive stresses upon themagnetic material 320, and 220, respectively, resulting in thevertically compressed free region 120 _(VC) exhibiting a lowered IMA_(L)and the vertically compressed fixed region 110 _(VC) exhibiting a higherIMA_(H) in magnetic cell structure 1500B.

In other embodiments, the magnetic material 220 exhibiting positivemagnetostriction or the magnetic material 320 exhibiting negativemagnetostriction is utilized to form both the fixed region 110 and thefree region 120, while the upper stressor structure 781 and the lowerstressor structure 782 are configured to be oppositely altered indimension during switching. For example, as illustrated in FIGS. 16A and16B, a magnetic cell structure 1600A of an in-plane STT-MRAM cell mayinclude a magnetic cell core 1601 having a fixed region 110 and a freeregion 120 formed of the magnetic material 220 exhibiting positivemagnetostriction. The upper stressor structure 781 may be configured tovertically contract, in the direction of arrow V_(C) of FIG. 16B,resulting in a vertically contracted stressor structure 781 _(VC), whilethe lower stressor structure 782 may be configured to vertically expand,in the direction of arrow V_(E), resulting in the vertically expandedfree region 120 _(VE) of magnetic cell structure 1600B having a loweredIMA_(L) and the vertically compressed fixed region 110 _(VC) having ahigher IMA_(H).

Accordingly, disclosed is a memory cell comprising a magnetic cell core.The magnetic cell core comprises a free region configured to exhibit aswitchable magnetic orientation. The magnetic cell core also comprises afixed region configured to exhibit a fixed magnetic orientation. Anonmagnetic region is disposed between the free region and the fixedregion. A stressor structure, proximate to the free region, isconfigured to change in size during switching of the switchable magneticorientation to exert a stress upon the free region during switching.Another stressor structure, proximate to the fixed region, is configuredto change in size during switching of the switchable magneticorientation to exert a stress upon the fixed region during switching.

With respect to any of the embodiments in which more than one stressorstructure is included in the magnetic cell core, it is contemplated thatthe stressor structure configured to exert a stress upon the free region120 (e.g., the upper stressor structure 781) may be configured to exerta stress that will result in a lowered MA of the free region 120 whilethe stressor structure configured to exert a stress upon the fixedregion 110 (e.g., the lower stressor structure 782) may be configured toexert a stress that will result in a higher MA of the fixed region 110.However, it is also contemplated that, in other embodiments, it may bedesirable to increase the MA strength of both the fixed region 110 andthe free region 120 or to decrease the MA strength of both the freeregion 120 and the fixed region 110. In such embodiments, the magneticmaterial from which the magnetic regions are formed may be selected tohave an appropriate magnetostriction (e.g., either positive or negative)and the stressor structures (e.g., the upper stressor structure 781 andthe lower stressor structure 782) configured to vertically expand,vertically contract, laterally expand, laterally contract, or anycombination thereof to impart the appropriate stress (e.g., verticaltensile, vertical compressive, lateral tensile, lateral compressive, orany combination thereof, respectively) to effect the desired alterationin the MA strength of the magnetic material.

In some embodiments, the stressor structure (e.g., any of the stressorstructure 180 (FIGS. 1 through 6C), the upper stressor structure 781(FIGS. 7 through 16B), and the lower stressor structure 782 (FIGS. 7through 16B)) may be configured as a multi-region stressor structure1780 with multiple stressor sub-regions 1781, as illustrated in FIG. 17.Each of the upper stressor structures 781 may be formed of a differentmaterial or of the same material in different discrete regions overlyingone another or arranged side-by-side so as to form the multi-regionstressor structure 1780 configured to alter in at least one dimensionduring switching.

In some embodiments, the stressor structure (e.g., any of the stressorstructures 180 (FIGS. 1 through 6C), the upper stressor structure 781(FIGS. 7 through 16B), and the lower stressor structure 782 (FIGS. 7through 16B)) may be formed as a continuous, uniform region proximate toone of the fixed region 110 and the free region 120. However, in otherembodiments, such as that illustrated in FIG. 18, the stressor structure(e.g., any of the stressor structures 180 (FIGS. 1 through 6C), theupper stressor structure 781 (FIGS. 7 through 16B), and the lowerstressor structure 782 (FIGS. 7 through 16B)) may be configured as adiscontinuous stressor structure 1880, with multiple discrete stressorfeatures 1881 separated from one another by spaces 1882. In suchembodiments, each of the discrete stressor features 1881 may beconfigured to alter in at least one dimension during switching to as toexert a stress upon neighboring magnetic material.

In some embodiments, the stressor structure (e.g., any of the stressorstructure 180 (FIGS. 1 through 6C), the upper stressor structure 781(FIGS. 7 through 16B), and the lower stressor structure 782 (FIGS. 7through 16B)) may be disposed directly on a magnetic region (e.g., thefixed region 110 or the free region 120). In such embodiments, expansionor contraction of the stressor structure (e.g., any of the stressorstructure 180 (FIGS. 1 through 6C), the upper stressor structure 781(FIGS. 7 through 16B), and the lower stressor structure 782 (FIGS. 7through 16B)) may exert a stress directly upon the neighboring magneticregion.

In other embodiments, such as that illustrated in FIG. 19, anintermediate structure 1990 may be disposed between the stressorstructure 180 and the neighboring magnetic material (e.g., the freeregion 120). In some such embodiments, the stressor structure 180 may bebetween the oxide capping region 170 and the intermediate structure1990. In other such embodiments, the oxide capping region 170 may bebetween the stressor structure 180 and the free region 120 so that theoxide capping region 170 serves as the intermediate structure 1990.Thus, the stressor structure 180 may be between the oxide capping region170 and the upper intermediary regions 150 (FIG. 1). If the upperintermediary regions 150 (FIG. 1) are not included, the stressorstructure 180 may be between the oxide capping region 170 and the upperelectrode 104 (FIG. 1). Accordingly, stress exerted by the stressorstructure 180 on the magnetic material may be imparted via theintermediate structure 1990.

In some embodiments, the magnetic cell core (e.g., the magnetic cellcore 101 (FIG. 1), the magnetic cell core 401 (FIG. 4), the magneticcell core 701 (FIG. 7), the magnetic cell core 1001 (FIGS. 10A and 10B),the magnetic cell core 1101 (FIGS. 11A and 11B), the magnetic cell core1201 (FIG. 12), the magnetic cell core 1501 (FIGS. 15A and 15B), and themagnetic cell core 1601 (FIGS. 16A and 16B)) may also include a heaterstructure 2090, as illustrated in FIG. 20. The heater structure 2090 maybe formed from, for example and without limitation, metal oxides, metalnitrides, metal oxynitrides, or any combination thereof. The heaterstructure 2090 may be configured to transfer heat either to or from thestressor structure 180 so as to enhance the alteration of the stressorstructure 180 during switching. For example, in embodiments in which thestressor structure 180 is configured to expand, the heater structure2090 may be configured to transfer heat to the stressor structure 180 toexpand the stressor structure 180 during switching even more than itwould otherwise expand in the absence of the heater structure 2090. Inembodiments in which the stressor structure 180 is configured tocontract, the heater structure 2090 may be configured to cool thestressor structure 180, such that heat transfers from the stressorstructure 180 to the heater structure 2090, to contract the stressorstructure 180 during switching even more than it would otherwisecontract in the absence of the heater structure 2090. As such, theheater structure 2090 may be operably connected to a heating element ora cooling element to enable the heat exchange between the heaterstructure 2090 and the stressor structure 180.

It should be noted that while the figures illustrate the free region 120to be disposed above the fixed region 110, the free region 120 and thefixed region 110 may be otherwise disposed relative to one another. Forexample, any of the magnetic cell cores (e.g., the magnetic cell core101 (FIG. 1), the magnetic cell core 401 (FIG. 4), the magnetic cellcore 701 (FIG. 7), the magnetic cell core 1001 (FIGS. 10A and 10B), themagnetic cell core 1101 (FIGS. 11A and 11B), the magnetic cell core 1201(FIG. 12), the magnetic cell core 1501 (FIGS. 15A and 15B), and themagnetic cell core 1601 (FIGS. 16A and 15B)) may be inverted between theupper electrode 104 and the lower electrode 105 and still be within thescope of the present disclosure.

The materials of the magnetic cell structure (e.g., the magnetic cellstructure 100 (FIG. 1), the magnetic cell structure 400 (FIG. 4), themagnetic cell structure 700 (FIG. 7), the magnetic cell structure 1000A(FIG. 10A), the magnetic cell structure 1100A (FIG. 11A), the magneticcell structure 1200 (FIG. 12), the magnetic cell structure 1500A (FIG.15A), and the magnetic cell structure 1600A (FIG. 16A)) may besequentially formed, one on top of the other, from base to top and thenpatterned to form the structures, with the lower electrode 105 and theupper electrode 104 formed therebelow and thereabove. Methods forforming and patterning the materials of the regions and structures, asdescribed above, are well known in the art and are not discussed indetail herein.

Accordingly, disclosed is a method of forming a memory cell. The methodcomprises forming a magnetic material over a substrate. A nonmagneticmaterial is formed over the magnetic material, and another magneticmaterial is formed over the nonmagnetic material. A stressor material isformed proximate to at least one of the magnetic material and theanother magnetic material. The stressor material has a coefficient ofthermal expansion differing from a coefficient of thermal expansion of anearest one of the magnetic material and the another magnetic material.

With reference to FIG. 21, illustrated is an STT-MRAM system 2100 thatincludes peripheral devices 2112 in operable communication with anSTT-MRAM cell 2114, a grouping of which may be fabricated to form anarray of memory cells in a grid pattern including a number of rows andcolumns, or in various other arrangements, depending on the systemrequirements and fabrication technology. The STT-MRAM cell 2114 includesa magnetic cell core 2102, an access transistor 2103, a conductivematerial that may function as a data/sense line 2104 (e.g., a bit line),a conductive material that may function as an access line 2105 (e.g., aword line), and a conductive material that may function as a source line2106. The peripheral devices 2112 of the STT-MRAM system 2100 mayinclude read/write circuitry 2107, a bit line reference 2108, and asense amplifier 2109. The cell core 2102 may be any one of the magneticcell cores (e.g., magnetic cell core 101 (FIG. 1), magnetic cell core401 (FIG. 4), magnetic cell core 701 (FIG. 7), magnetic cell core 1001(FIGS. 10A and 10B), magnetic cell core 1101 (FIGS. 11A and 11B),magnetic cell core 1201 (FIG. 12), magnetic cell core 1501 (FIGS. 15Aand 15B), and magnetic cell core 1601 (FIGS. 16A and 16B)) describedabove. Due to the structure of the cell core 2102, i.e., the inclusionof at least one stressor structure 180, 781, 782) an MA strength of amagnetic region within the cell core 2102 may be altered duringswitching, e.g., to enable use of a lower switching current.

In use and operation, when an STT-MRAM cell 2114 is selected to beprogrammed, a programming current is applied to the STT-MRAM cell 2114,and the current is spin-polarized by the fixed region of the cell core2102 and exerts a torque on the free region of the cell core 2102, whichswitches the magnetization of the free region to “write to” or “program”the STT-MRAM cell 2114. In a read operation of the STT-MRAM cell 2114, acurrent is used to detect the resistance state of the cell core 2102.

To initiate programming of the STT-MRAM cell 2114, the read/writecircuitry 2107 may generate a write current (i.e., a programmingcurrent) to the data/sense line 2104 and the source line 2106. Thepolarity of the voltage between the data/sense line 2104 and the sourceline 2106 determines the switch in magnetic orientation of the freeregion in the cell core 2102. By changing the magnetic orientation ofthe free region with the spin polarity, the free region is magnetizedaccording to the spin polarity of the programming current, theprogrammed logic state is written to the STT-MRAM cell 2114.

To read the STT-MRAM cell 2114, the read/write circuitry 2107 generatesa read voltage to the data/sense line 2104 and the source line 2106through the cell core 2102 and the access transistor 2103. Theprogrammed state of the STT-MRAM cell 2114 relates to the electricalresistance across the cell core 2102, which may be determined by thevoltage difference between the data/sense line 2104 and the source line2106. In some embodiments, the voltage difference may be compared to thebit line reference 2108 and amplified by the sense amplifier 2109.

FIG. 21 illustrates one example of an operable STT-MRAM system 2100. Itis contemplated, however, that the magnetic cell cores (e.g., magneticcell core 101 (FIG. 1), magnetic cell core 401 (FIG. 4), magnetic cellcore 701 (FIG. 7), magnetic cell core 1001 (FIGS. 10A and 10B), magneticcell core 1101 (FIGS. 11A and 11B), magnetic cell core 1201 (FIG. 12),magnetic cell core 1501 (FIGS. 15A and 15B), and magnetic cell core 1601(FIGS. 16A and 16B)) may be incorporated and utilized within anySTT-MRAM system configured to incorporate a magnetic cell core havingmagnetic regions.

Accordingly, disclosed is a spin torque transfer magnetic random accessmemory (STT-MRAM) system comprising a magnetic cell core comprising astressor structure proximate to a magnetic region. The stressorstructure is configured to exert a stress upon the magnetic region inresponse to a current passed through the stressor structure in themagnetic cell core during switching to alter an electrical resistanceacross the magnetic region. The STT-MRAM system also comprisesconductive materials in operable communication with the magnetic cellcore.

With reference to FIG. 22, illustrated is a simplified block diagram ofa semiconductor device 2200 implemented according to one or moreembodiments described herein. The semiconductor device 2200 includes amemory array 2202 and a control logic component 2204. The memory array2202 may include a plurality of the STT-MRAM cells 2114 (FIG. 21)including any of the magnetic cell cores (e.g., magnetic cell core 101(FIG. 1), magnetic cell core 401 (FIG. 4), magnetic cell core 701 (FIG.7), magnetic cell core 1001 (FIGS. 10A and 10B), magnetic cell core 1101(FIGS. 11A and 11B), magnetic cell core 1201 (FIG. 12), magnetic cellcore 1501 (FIGS. 15A and 15B), and magnetic cell core 1601 (FIGS. 16Aand 16B)) discussed above, which magnetic cell cores (e.g., magneticcell core 101 (FIG. 1), magnetic cell core 401 (FIG. 4), magnetic cellcore 701 (FIG. 7), magnetic cell core 1001 (FIGS. 10A and 10B), magneticcell core 1101 (FIGS. 11A and 11B), magnetic cell core 1201 (FIG. 12),magnetic cell core 1501 (FIGS. 15A and 15B), and magnetic cell core 1601(FIGS. 16A and 16B)) may have been formed according to a methoddescribed above and may be operated according to a method describedabove. The control logic component 2204 may be configured to operativelyinteract with the memory array 2202 so as to read from or write to anyor all memory cells (e.g., STT-MRAM cell 2114 (FIG. 21)) within thememory array 2202.

Accordingly, disclosed is a semiconductor device comprising a spintorque transfer magnetic random access memory (STT-MRAM) arraycomprising STT-MRAM cells. An STT-MRAM cell of the STT-MRAM cellscomprises a magnetic cell core. The magnetic cell core comprises anonmagnetic region between a magnetic region and another magneticregion. The magnetic cell core also comprises a stressor structureproximate to the magnetic region. The stressor structure has a differentcoefficient of thermal expansion than the magnetic region and isconfigured to alter in at least one dimension and exert a stress uponthe magnetic region when subjected to a programming current duringswitching of the STT-MRAM cell to alter a magnetic anisotropy of themagnetic region.

With reference to FIG. 23, depicted is a processor-based system 2300.The processor-based system 2300 may include various electronic devicesmanufactured in accordance with embodiments of the present disclosure.The processor-based system 2300 may be any of a variety of types such asa computer, pager, cellular phone, personal organizer, control circuit,or other electronic device. The processor-based system 2300 may includeone or more processors 2302, such as a microprocessor, to control theprocessing of system functions and requests in the processor-basedsystem 2300. The processor 2302 and other subcomponents of theprocessor-based system 2300 may include magnetic memory devicesmanufactured in accordance with embodiments of the present disclosure.

The processor-based system 2300 may include a power supply 2304. Forexample, if the processor-based system 2300 is a portable system, thepower supply 2304 may include one or more of a fuel cell, a powerscavenging device, permanent batteries, replaceable batteries, andrechargeable batteries. The power supply 2304 may also include an ACadapter; therefore, the processor-based system 2300 may be plugged intoa wall outlet, for example. The power supply 2304 may also include a DCadapter such that the processor-based system 2300 may be plugged into avehicle cigarette lighter or a vehicle power port, for example.

Various other devices may be coupled to the processor 2302 depending onthe functions that the processor-based system 2300 performs. Forexample, a user interface 2306 may be coupled to the processor 2302. Theuser interface 2306 may include input devices such as buttons, switches,a keyboard, a light pen, a mouse, a digitizer and stylus, a touchscreen, a voice recognition system, a microphone, or a combinationthereof. A display 2308 may also be coupled to the processor 2302. Thedisplay 2308 may include an LCD display, an SED display, a CRT display,a DLP display, a plasma display, an OLED display, an LED display, athree-dimensional projection, an audio display, or a combinationthereof. Furthermore, an RF sub-system/baseband processor 2310 may alsobe coupled to the processor 2302. The RF sub-system/baseband processor2310 may include an antenna that is coupled to an RF receiver and to anRF transmitter (not shown). A communication port 2312, or more than onecommunication port 2312, may also be coupled to the processor 2302. Thecommunication port 2312 may be adapted to be coupled to one or moreperipheral devices 2314, such as a modem, a printer, a computer, ascanner, or a camera, or to a network, such as a local area network,remote area network, intranet, or the Internet, for example.

The processor 2302 may control the processor-based system 2300 byimplementing software programs stored in the memory. The softwareprograms may include an operating system, database software, draftingsoftware, word processing software, media editing software, or mediaplaying software, for example. The memory is operably coupled to theprocessor 2302 to store and facilitate execution of various programs.For example, the processor 2302 may be coupled to system memory 2316,which may include one or more of spin torque transfer magnetic randomaccess memory (STT-MRAM), magnetic random access memory (MRAM), dynamicrandom access memory (DRAM), static random access memory (SRAM),racetrack memory, and other known memory types. The system memory 2316may include volatile memory, non-volatile memory, or a combinationthereof. The system memory 2316 is typically large so that it can storedynamically loaded applications and data. In some embodiments, thesystem memory 2316 may include semiconductor devices, such as thesemiconductor device 2200 of FIG. 22, memory cells including any ofmagnetic cell cores (e.g., magnetic cell core 101 (FIG. 1), magneticcell core 401 (FIG. 4), magnetic cell core 701 (FIG. 7), magnetic cellcore 1001 (FIGS. 10A and 10B), magnetic cell core 1101 (FIGS. 11A and11B), magnetic cell core 1201 (FIG. 12), magnetic cell core 1501 (FIGS.15A and 15B), and magnetic cell core 1601 (FIGS. 16A and 16B)), or acombination thereof.

The processor 2302 may also be coupled to non-volatile memory 2318,which is not to suggest that system memory 2316 is necessarily volatile.The non-volatile memory 2318 may include one or more of STT-MRAM, MRAM,read-only memory (ROM) such as an EPROM, resistive read-only memory(RROM), and Flash memory to be used in conjunction with the systemmemory 2316. The size of the non-volatile memory 2318 is typicallyselected to be just large enough to store any necessary operatingsystem, application programs, and fixed data. Additionally, thenon-volatile memory 2318 may include a high capacity memory such as diskdrive memory, such as a hybrid-drive including resistive memory or othertypes of non-volatile solid-state memory, for example. The non-volatilememory 2318 may include semiconductor devices, such as the semiconductordevice 2200 of FIG. 22, memory cells including any of magnetic cellcores (e.g., magnetic cell core 101 (FIG. 1), magnetic cell core 401(FIG. 4), magnetic cell core 701 (FIG. 7), magnetic cell core 1001(FIGS. 10A and 10B), magnetic cell core 1101 (FIGS. 11A and 11B),magnetic cell core 1201 (FIG. 12), magnetic cell core 1501 (FIGS. 15Aand 15B), and magnetic cell core 1601 (FIGS. 16A and 16B)), or acombination thereof.

While the present disclosure is susceptible to various modifications andalternative forms in implementation thereof, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. However, the present disclosure is not intended to belimited to the particular forms disclosed. Rather, the presentdisclosure encompasses all modifications, combinations, equivalents,variations, and alternatives falling within the scope of the presentdisclosure as defined by the following appended claims and their legalequivalents.

What is claimed is:
 1. A memory cell comprising: a magnetic cell coreextending vertically between a pair of neighboring electrodes betweenwhich a programming current is passable through the magnetic cell core,the magnetic cell core comprising: a magnetic region; and a stressorstructure vertically between the pair of neighboring electrodes andconfigured to vertically expand or vertically contract, relative to aneighboring material and responsive to an increase in temperature, toexert a vertical stress upon the magnetic region and to alter a magneticanisotropy of the magnetic region when the stressor structure issubjected to the programming current passing through the magnetic cellcore during switching of a magnetic orientation of the magnetic region.2. The memory cell of claim 1, wherein the magnetic region exhibits avertical magnetic orientation.
 3. The memory cell of claim 2, whereinthe magnetic region comprises a magnetic material exhibiting positivemagnetostriction.
 4. The memory cell of claim 3, wherein the stressorstructure is configured to vertically expand, relative to theneighboring material and responsive to the increase in temperature, toexert a vertical compressive stress upon the magnetic region and toreduce a perpendicular magnetic anisotropy of the magnetic region whenthe stressor structure is subjected to the programming current passingthrough the magnetic cell core during switching.
 5. The memory cell ofclaim 1, wherein the stressor structure is configured to verticallycontract, relative to the neighboring material and responsive to theincrease in temperature, to exert a vertical tensile stress upon themagnetic region and to reduce a perpendicular magnetic anisotropy of themagnetic region when the stressor structure is subjected to theprogramming current passing through the magnetic cell core duringswitching, the magnetic region exhibiting a predominantly verticalmagnetic orientation.
 6. The memory cell of claim 1, wherein: themagnetic region exhibits a horizontal magnetic orientation; the magneticregion comprises a magnetic material exhibiting negativemagnetostriction; and the stressor structure is configured to verticallyexpand when subjected to the programming current to reduce an in-planemagnetic anisotropy of the magnetic region.
 7. The memory cell of claim1, wherein: the magnetic region exhibits a horizontal magneticorientation; the magnetic region comprises a magnetic materialexhibiting positive magnetostriction; and the stressor structure isconfigured to vertically contract when subjected to the programmingcurrent to reduce an in-plane magnetic anisotropy of the magneticregion.
 8. The memory cell of claim 1, wherein the magnetic cell corefurther comprises an intermediate structure between the magnetic regionand the stressor structure.
 9. The memory cell of claim 1, wherein thestressor structure is a discontinuous stressor structure.
 10. The memorycell of claim 1, wherein: the magnetic region is formulated to exhibit aswitchable magnetic orientation; the stressor structure is configured toexert the vertical stress upon the magnetic region when the stressorstructure is subjected to the programming current to lower the magneticanisotropy of the magnetic region; and the magnetic cell core furthercomprises: another magnetic region formulated to exhibit a fixedmagnetic orientation; a nonmagnetic region between the magnetic regionand the another magnetic region; and another stressor structureconfigured to exert another stress upon the another magnetic region whenthe another stressor structure is subjected to the programming currentpassing through the magnetic cell core to increase a magnetic anisotropyof the another magnetic region.
 11. The memory cell of claim 10, whereinat least one of the stressor structure and the another stressorstructure comprise a metal.
 12. The memory cell of claim 11, wherein themetal is selected from the group consisting of aluminum and copper. 13.The memory cell of claim 11, wherein: both the magnetic region and theanother magnetic region are formed from a magnetic material exhibiting amagnetostriction independently selected from the group consisting ofpositive magnetostriction and negative magnetostriction; and thestressor structure is configured to vertically expand or verticallycontract and the another stressor structure is configured to verticallycontract or vertically expand, respectively, when subjected to theprogramming current to exert oppositely-directed stress upon themagnetic region and the another magnetic region, respectively.
 14. Thememory cell of claim 11, wherein: the magnetic region and the anothermagnetic region are formed from magnetic materials exhibiting differentmagnetostriction selected from the group consisting of positivemagnetostriction and negative magnetostriction; and the stressorstructure is configured to vertically expand or vertically contract andthe another stressor structure is configured to vertically expand orvertically contract, respectively when subjected to the programmingcurrent to exert the same direction of stress upon the magnetic regionand the another magnetic region, respectively.
 15. A memory cellcomprising: a magnetic cell core comprising: a magnetic regioncomprising a magnetic material exhibiting negative magnetostriction anda predominantly vertical magnetic orientation; and a stressor structureconfigured to laterally contract, exert a lateral compressive stressupon the magnetic region, and to reduce a perpendicular magneticanisotropy of the magnetic region when the stressor structure issubjected to a programming current passing through the magnetic cellcore during switching of the predominantly vertical magnetic orientationof the magnetic region.
 16. A method of operating a spin torque transfermagnetic random access memory (STT-MRAM) cell, the method comprising:providing an STT-MRAM cell comprising a magnetic cell core extendingvertically between a pair of neighboring electrodes between which aprogramming current is passable through the magnetic cell core, themagnetic cell core comprising a magnetic region and a stressor structurevertically between the pair of neighboring electrodes and configured tovertically expand or vertically contract, relative to a neighboringmaterial and responsive to an increase in temperature, to exert avertical stress upon the magnetic region and to alter a magneticanisotropy of the magnetic region when the stressor structure issubjected to the programming current passing through the magnetic cellcore during switching of a magnetic orientation of the magnetic region;and altering an electrical resistance across the magnetic region andanother magnetic region of the magnetic cell core of the STT-MRAM cellto program a logic state of the STT-MRAM cell, comprising: switching themagnetic orientation of the magnetic region, comprising passing theprogramming current between the pair of neighboring electrodes andthrough the magnetic cell core; and responsive at least in part to theincrease in temperature while passing the current, vertically expandingor vertically contracting the stressor structure, relative to theneighboring material, proximate to the magnetic region to exert thevertical stress upon the magnetic region and to alter the magneticanisotropy of the magnetic region.
 17. The method of claim 16, whereinvertically expanding or vertically contracting the stressor structurecomprises vertically expanding the stressor structure proximate to themagnetic region to lower the magnetic anisotropy of the magnetic region,the magnetic region configured as a free region of the magnetic cellcore.
 18. The method of claim 16, further comprising retaining theelectrical resistance across the magnetic region and the anothermagnetic region to store the logic state of the STT-MRAM cell,comprising removing the vertical stress upon the magnetic region torevert the magnetic anisotropy of the magnetic region to a storagestate.
 19. A method of forming a memory cell, the method comprising:forming a lower electrode supported by a substrate; forming a magneticcell core over the lower electrode, forming the magnetic cell corecomprising: forming a magnetic region over a substrate; forming anonmagnetic region over the magnetic region; forming another magneticregion over the nonmagnetic region; and forming a stressor structureproximate to the magnetic region, the stressor structure comprising astressor material having a coefficient of thermal expansion differingfrom a coefficient of thermal expansion of the magnetic region, thestressor structure being configured to vertically expand or verticallycontract, relative to a neighboring material and responsive to anincrease in temperature, to exert a vertical stress upon the magneticregion and to alter a magnetic anisotropy of the magnetic region whenthe stressor structure is subjected to a programming current passingthrough the magnetic cell core during switching of a magneticorientation of the magnetic region; and forming an upper electrode overthe magnetic cell core, the magnetic cell core extending verticallybetween the lower electrode and the upper electrode, the lower electrodeand the upper electrode being a pair of neighboring electrodes betweenwhich the programming current is passable through the magnetic cellcore.
 20. The method of claim 19, wherein forming the magnetic cell corefurther comprises forming another stressor material proximate to theanother magnetic region.
 21. A semiconductor device, comprising: a spintorque transfer magnetic random access memory (STT-MRAM) arraycomprising: STT-MRAM cells, an STT-MRAM cell of the STT-MRAM cellscomprising: a magnetic cell core extending vertically between a pair ofneighboring electrodes between which a programming current is passablethrough the magnetic cell core, the magnetic cell core comprising: anonmagnetic region between a magnetic region and another magneticregion; and a stressor structure vertically between the pair ofneighboring electrodes and proximate to the magnetic region, thestressor structure having a different coefficient of thermal expansionthan the magnetic region, the stressor structure configured to alter inat least a vertical dimension responsive to an increase in temperatureand configured to exert a vertical stress upon the magnetic region whensubjected to the programming current during switching of the STT-MRAMcell to alter a magnetic anisotropy of the magnetic region.
 22. Thesemiconductor device of claim 21, wherein a material of the stressorstructure has a coefficient of thermal expansion at least about 0.1%greater than or at least about 0.1% less than a coefficient of thermalexpansion of the magnetic region.
 23. A spin torque transfer magneticrandom access memory (STT-MRAM) system, comprising: a magnetic cell corecomprising a stressor structure proximate to a magnetic regioncomprising a magnetic material exhibiting negative magnetostriction, thestressor structure configured to alter in size and exert a stress uponthe magnetic region in response to a current passed through the stressorstructure in the magnetic cell core during switching to alter anelectrical resistance across the magnetic region, the magnetic regionconfigured to, responsive to the stress and during the switching,exhibit an increased magnetic anisotropy strength in a direction of apredominant magnetic orientation exhibited by the magnetic region,relative to a magnetic anisotropy strength in the direction exhibitedduring storage; and conductive materials in operable communication withthe magnetic cell core.
 24. The STT-MRAM system of claim 23, wherein thestressor structure is configured to laterally expand and exert a lateraltensile stress upon the magnetic region in response to the currentpassed through the stressor structure in the magnetic cell core duringswitching, the magnetic region configured to, responsive to the lateraltensile stress and during the switching, exhibit an increasedperpendicular magnetic anisotropy strength, the magnetic regionexhibiting a predominantly vertical magnetic orientation.